Singing off the same hymn sheet? Examining coherence in a talent development pathway (part 2)

Existing literature highlights the common characteristics of successful talent development environments, notably the need for long-term development, individual athlete attention, communication, alignment, and psycho-behavioural development. Little is known however about the complex talent development environment of an international sport organisation where multiple contexts and various stakeholders exist. Considering the lack of research relating to females in talent development, we examined a female national hockey talent development environment and more specifically the level of coherence that existed within the talent development environment from different stakeholder perspectives. Twenty-seven international female hockey players and fourteen pathway staff members from across the talent development pathway participated in semi-structured focus groups. An inductive-deductive thematic analysis was conducted. Results suggest that the talent development environment provides a long-term development experience supplemented with individual athlete attention at international level. However, a general lack of coherence and systematic development was evident across the talent development environment contexts with varying levels of coherence found within the higher-order themes of appropriate development, not early success, individualised and ongoing development, and wide-ranging coherent messages and support. This highlights a need for improved direction from the National Governing Body if systematic coherence towards talent development is to be achieved.

Creating a Digital Toolkit to Reduce Fatigue and Promote Quality of Life in Multiple Sclerosis: Participatory Design and Usability Study

Background

Fatigue is one of the most common and debilitating symptoms of multiple sclerosis (MS), experienced by more than 80% of people with MS. FACETS (Fatigue: Applying Cognitive Behavioral and Energy Effectiveness Techniques to Lifestyle) is an evidence-based, face-to-face, 6-session group fatigue management program for people with MS. Homework tasks are an integral part of FACETS and are currently undertaken in a paper-based form. Feedback from a consultation undertaken with FACETS attendees and health care professionals with experience in delivering the FACETS program suggested that being able to complete the homework tasks digitally would be desirable, potentially enhancing engagement and adherence and enabling on-the-go access to fit into busy lifestyles. Relative to other long-term conditions, there are few apps specifically for MS and, of those available, many have been developed with little or no input from people with MS.

Objective

The purpose of this mixed methods study was to create a digital toolkit comprising the homework tasks (eg, activity diary, goal planner, thought diary) of the FACETS program for people with MS, considering end users’ unique requirements throughout the design, build, prototyping, and testing stages.

Methods

Phase 1 involved the elicitation of detailed user requirements for the toolkit via 2 focus groups with previous attendees of FACETS (n=3 and n=6) and wireframing. Phase 2 involved supervised usability testing with people with MS (n=11) with iterative prototyping. The usability sessions involved going through test scenarios using the FACETS toolkit on an Android test phone with video capture and concurrent think-aloud followed by completion of the System Usability Scale (SUS) and a semistructured interview collecting feedback about design, content, and functionality.

Results

The mean SUS score for the digital toolkit was 74.3 (SD 16.8, 95% CI 63.2-85.6; range 37.5-95), which equates to an adjective rating of good and a B grade (70th-79th percentile range) on the Sauro-Lewis curved grading scale. A number of usability and design issues (such as simplifying overall screen flow to better meet users’ needs) and suggestions for improvements (such as using location-based services and displaying personalized information and progress via a central dashboard) were addressed and implemented during the usability testing cycle.

Conclusions

This work highlights the importance of the participation of people with MS across the entire development cycle, working to a human-centered design methodology to enable a considered and MS-centered solution to be developed. Continued horizon scanning for emergent technological enhancements will enable us to identify opportunities for further improvements to the FACETS toolkit prior to launch. The toolkit supports self-monitoring and management of fatigue and has potential applicability to other long-term conditions where fatigue is a significant issue.

Singing off the same hymn sheet? Examining coherence in a talent development pathway (part 1)

Although there is research available into successful Talent Development Environments (TDEs), the data mostly reflects TDEs in elite academies, national groups or in a single successful club. This literature provides insight into the positive characteristics that are commonplace in these effective TDEs. However, little is known about the TDE surrounding an entire amateur national organization where athletes regularly compete across multiple teams, simultaneously representing at both domestic and international level. Importantly this added complexity increases the number of stakeholders across the pathway (e.g., school, club, international) creating a need for coherence throughout the TDE. Additionally considering the lack of research relating to females in talent development, we were interested from a pragmatic view, in examining the TDE of an amateur national hockey organization where young female athletes must navigate the pathway while simultaneously playing on multiple teams, contending with various coaches and contexts. The results suggest that the TDE provides a long term development experience supplemented with a good support network across all contexts. However, the alignment of expectations across contexts and the quality preparation of athletes in this TDE requires more attention to facilitate effective holistic athlete development.

Monitoring Wellness, Training Load, and Running Performance During a Major International Female Field Hockey Tournament

McGuinness, McMahon, G, A, Malone, S, Kenna, D, Passmore, D, and Collins, K. Monitoring wellness, training load, and running performance during a major international female field hockey tournament. J Strength Cond Res 34(8): 2312-2320, 2020-The current observational study quantified players' activity profiles during a major international female field hockey tournament and determined whether an association exists between well-being measures and running performance within elite female hockey players. Elite female field hockey players (23 ± 3 years; 162.6 ± 13 cm; and 66 ± 6 kg) participated in the study. Participants running performance was monitored using global positioning system technology (S5; Catapult Innovations, Scoresby, Victoria, Australia), with daily well-being questionnaires used to quantify player responses during the tournament. Thresholds for the magnitude of the observed change for each variable were determined using the Hopkins Spreadsheets for analysis of controlled trials. Relative distance (m·min) was likely lower when compared with game 1 in game 7. Relative high speed (m·min >16 km·h) was likely lower in games 5, 6, and 7 when compared with game 1. Subjective load was very likely higher in game 2 and very likely lower in game 3 when compared with game 1. Mood and sleep quality were likely lower in game 1 when compared with game 4 and game 7. Muscle soreness was likely higher when compared with game 1 in game 7. During the tournament, it was observed that a decrease in players' daily well-being was accompanied by changes in running performance. Furthermore, changes to players' muscle soreness and sleep quality result in decreased players' high-speed running performance during match-play. Therefore, to prevent the observed effects, coaches should adopt strategies to enhance sleep quality and incorporate specific recovery modalities to reduce musculoskeletal soreness.

Chemical Modification of Linkers Provides Stable Linker-Payloads for the Generation of Antibody-Drug Conjugates

Stability of antibody-drug conjugates (ADCs) in mouse serum is one of the critical requirements for the evaluation of ADCs in mouse tumor models. Described herein is a strategy to address the mouse serum instability of uncialamycin linker-payloads through various chemical approaches that involve modification of different parts of the linker and payload. This effort ultimately led to the identification of a m-amide p-aminobenzyl carbamate (MA-PABC) group that resulted in linkers with dramatic improvement of mouse serum stability without affecting the desired proteolytic cleavage.

Design, Synthesis, and Structure-Activity Relationships of Novel Tetrahydroisoquinolino Benzodiazepine Dimer Antitumor Agents and Their Application in Antibody-Drug Conjugates

A series of tetrahydroisoquinoline-based benzodiazepine dimers were synthesized and tested for in vitro cytotoxicity against a panel of cancer cell lines. Structure-activity relationship investigation of various spacers guided by molecular modeling studies helped to identify compounds with picomolar activity. Payload 17 was conjugated to anti-mesothelin and anti-fucosylated monosialotetrahexosylganglioside (FucGM1) antibodies using lysosome-cleavable valine-citrulline dipeptide linkers via heterogeneous lysine conjugation and bacterial transglutaminase-mediated site-specific conjugation. In vitro, these antibody drug conjugates (ADCs) exhibited significant cytotoxic and target-mediated selectivity on human cancer cell lines. The pharmacokinetics and efficacy of these ADCs were further evaluated in gastric and lung cancer xenograft models in mice. Consistent pharmacokinetic profiles, high target specificity, and robust antitumor activity were observed in these models after a single dose of the ADC-46 (0.02 μmol/kg).

Synthesis and Biological Evaluation of a Carbamate-Containing Tubulysin Antibody-Drug Conjugate

Antibody-drug conjugates (ADCs) use antibodies to deliver cytotoxic payloads directly into tumor cells via specifically binding to the target cell surface antigens. ADCs can enhance the anti-tumor effects of antibodies, and increase the delivery of cytotoxic payloads to cancer cells with a better therapeutic index. An ADC was prepared with a potent carbamate-containing tubulysin analogue attached to an anti-mesothelin antibody via a Cit-Val dipeptide linker. An aniline functionality in the tubulysin analogue was created to provide a site of linker attachment via an amide bond that would be stable in systemic circulation. Upon ADC internalization into antigen-positive cancer cells, the Cit-Val dipeptide linker was cleaved by lysosomal proteases, and the drug was released inside the tumor cells. The naturally occurring acetate of tubulysin was modified to a carbamate to reduce acetate hydrolysis of the ADC in circulation and to increase the hydrophilicity of the drug. The ADC bearing the monoclonal anti-mesothelin antibody and the carbamate-containing tubulysin was highly potent and immunologically specific to H226 human lung carcinoma cells in vitro, and efficacious at well-tolerated doses in a mesothelin-positive OVCAR3 ovarian cancer xenograft mouse model.

Peak Running Intensity of Elite Female Field Hockey Players During Competitive Match Play

McGuinness, A, Passmore, D, Malone, S, and Collins, K. Peak running intensity of elite female field hockey players during competitive match play. J Strength Cond Res XX(X): 000-000, 2020-In recent years, backroom coaching staff have relied heavily on the global demands of competitive match-play to monitor running performance within training and match environments. Although, these figures help prepare players for the demands of match-play, they do not account for the physical and physiological stress of the most intense periods of competition. The aim of the current study was to quantify the duration and position-specific maximal running performance during match-play using a 1-10-minute moving average epoch methodology. Twenty-six (n = 26) elite international female field hockey players (23 ± 3 years; 162.6 ± 13 cm; 66 ± 6 kg) participated in the current observational study. Data were collected during 22 international games, resulting in over 360 individual samples (n = 368) being obtained for analysis. Players were categorized based on their positional lines of play (defenders, midfielders, and forwards). Variables of interest included relative total (m·min), high-speed (>16 km·h; m·min) and sprint distance (>20 km·h; m·min). Regardless of position, varying differences were observed between 10-minute rolling average for relative total (mod-large), high-speed (mod-large), and sprint (mod-large) distance respectively. Furthermore, as the duration of the rolling average increased, so did the observed differences (small). The forwards (119.3 ± 19.7 m·min) were reported to have the highest peak output during minute one for relative high-speed distance when compared with the defenders (100.7 ± 19.7, effect size [ES] 0.9, large) and the midfield (106.8 ± 23.4 m·min, ES 0.5, moderate). The results of the current study show that the running performance of field hockey players alters during match-play irrespective of moving average. Finally, the data will aid practitioners in the development of sport-specific drills to adequately prepare hockey players for the maximal intensity periods of elite hockey match-play.

Physical Activity and Physiological Profiles of Elite International Female Field Hockey Players Across the Quarters of Competitive Match Play

McGuinness, A, Malone, S, Hughes, B, and Collins, K. Physical activity and physiological profiles of elite international female field hockey players across the quarters of competitive match play. J Strength Cond Res 33(9): 2513-2522, 2019-The aim of the current investigation was to quantify the physical and physiological demands of elite international female field hockey across the quarters of match-play. Twenty-seven elite international female field hockey outfield players (23 ± 3 years; 162.6 ± 13.0 cm; 66.0 ± 6.0 kg) participated in the current observational study during the 2016-2017 season. Participants were monitored using global positioning system technology and HR monitors. Players were categorized based on 3 different playing positions. Activity was categorized into total distance (in meters), relative total distance (m·min), low-, moderate-, and high-intensity distance (m), maximum velocity (km·h), and percentage maximal velocity (%). Physiological demands were quantified through players peak heart rate (HRPeak), which was classified based on the player's individual HRmax determined using a Yo-Yo intermittent recovery level 1 test. Players spent on average 38 ± 8 minutes in match play. The total distance covered was 4,847 ± 583 m (127.6 ± 15.6 m·min). Defenders covered a greater total distance across all 3 positions (p = ≤ 0.05). The midfielders covered a greater moderate-intensity distance (p ≤ 0.001), whereas the forwards covered more high-intensity distance (p ≤ 0.001). The HRpeak of the players was 198 ± 4 b·min with a mean exercise intensity of 95 ± 1% HRmax. The time spent >70% HRmax decreased significantly across the quarters (p = 0.01, η = 0.03). Defenders were found to spend more time >85% HRmax when compared with other positions (p ≤ 0.001, η = 0.28). The current study provides normative data that coaches should consider when developing training drills to better optimize the positional physical and physiological activity profiles that best replicate match play.

An Interactive Mobile Phone App (SMART 5-A-DAY) for Increasing Knowledge of and Adherence to Fruit and Vegetable Recommendations: Development and Pilot Randomized Controlled Trial

Background

Fruit and vegetable consumption is important for health, but many individuals fail to consume adequate amounts for health benefits. Although many individuals are aware of current fruit and vegetable consumption recommendations, research suggests that adherence to these is hampered by low knowledge of the details of these recommendations.

Objective

This paper reports the development and details of a pilot randomized controlled test of a novel interactive mobile phone app for addressing low knowledge of the UK 5-a-day fruit and vegetable recommendations.

Methods

Requirements for the app were first defined by researchers and potential end users and prioritized using the MoSCoW (Must have, Should have, Could have, Won’t have) method. Second, a prototype mobile phone app was developed using an agile approach. Third, the prototype app was tested in a randomized controlled pilot trial for impacts on knowledge and intake of fruit and vegetables. Volunteers were randomized to either receive (n=50) or not receive the app (n=44) for 2 or 4 weeks, and fruit and vegetable knowledge, intake, and behavior were assessed at the beginning of the study and after 1 and 2 weeks or after 2 and 4 weeks, respectively. App usage and qualitative feedback were also investigated. All findings then informed the development of a final app.

Results

Low knowledge of consumption recommendations centered around portion sizes and the need for variety, and an interactive mobile phone app was considered a suitable tool for improving this knowledge in a practical manner that would be available both at time of consumption and outside of these times. The pilot test revealed improved behavior after 2 weeks compared with baseline in volunteers who received the app, but improvements in knowledge on fruit and vegetable recommendations were found in both groups, and no improvements in fruit and vegetable intakes were found in formal measures. Patterns of app usage and qualitative feedback also suggested a number of modifications. The resultant final app incorporates several behavior change techniques (goal-setting, self-monitoring, and personalized feedback) as well as aiming to improve knowledge.

Conclusions

A novel interactive mobile phone app was successfully developed based on requirements, and when tested in a pilot randomized controlled trial, this app was found to have some impacts on fruit and vegetable outcomes. Although benefits from the app were small, impacts will likely increase as a result of recent modifications. The final SMART 5-A-DAY app is available in the Google Play Store and now needs testing in the target population.

Trial Registration

ClinicalTrials.gov NCT02779491; https://www.clinicaltrials.gov/ct2/show/NCT02779491

What About the Girls? Exploring the Gender Data Gap in Talent Development

Although there is an extensive literature about talent development, the lack of data pertaining to females is problematic. Indeed, the gender data gap can be seen in practically all domains including sport and exercise medicine. Evidence-based practice is the systematic reviewing of the best evidence in order to make informed choices about practice. Unfortunately, it may be that the data collected in sport is typically about male experiences, and not female; a rather unfortunate omission given that approximately half of the population is made up of women. When female athletes are underrepresented in research there are issues when making inferences about data collected in male dominated research domains to inform practice and policy for female athletes. In parallel, female sport participation is continually increasing worldwide. Recognizing the importance of evidence-based practice in driving policy and practice, and reflecting the gender data gap that is a consistent feature of (almost) all other domains, we were interested in examining whether a gender data gap exists in talent development research. The results suggest that a gender data gap exists in talent development research across all topics. Youth athlete development pathways may be failing to recognize the development requirements of females, particularly where female sports may be borrowing systems that are perceived to work for their male counterparts. In order to ensure robust evidence based practice in female youth sport there is a need to increase the visibility of female athletes in talent development literature.

Utility of Ion Mobility Mass Spectrometry for Drug-to-Antibody Ratio Measurements in Antibody-Drug Conjugates

Antibody-drug conjugates (ADCs) are emerging modalities in the pharmaceutical industry. Characterization of ADC's drug-to-antibody ratio (DAR) becomes a key assessment because of its importance in ADC efficacy and safety. DAR characterization by conventional intact protein MS analysis, however, is challenging because of high heterogeneity of ADC samples. The analysis often requires protein deglycosylation, disulfide-bond reduction, or partial fragmentation. In this study, we illustrate the practical utility of ion mobility mass spectrometry (IM-MS) in a routine LC/MS workflow for DAR measurements. This strategy allows analyte "cleanup" in the gas phase, providing significant improvement of signal-to-noise ratios of ADC intact mass spectra for accurate DAR measurements. In addition, protein drift time analysis offers a new dimension in monitoring the changes of DAR in lot-to-lot analysis.

Pharmacokinetic characterization of BMS-936561, an anti-CD70 antibody-drug conjugate, in preclinical animal species and prediction of its pharmacokinetics in humans

CD70 is a tumor necrosis factor (TNF)-like type II integral membrane protein that is transiently expressed on activated T- and B-lymphocytes. Aberrant expression of CD70 was identified in both solid tumors and haematologic malignancies. BMS-936561 (αCD70_MED-A) is an antibody-drug conjugate composed of a fully human anti-CD70 monoclonal antibody (αCD70) conjugated with a duocarmycin derivative, MED-A, through a maleimide-containing citrulline-valine dipeptide linker. MED-A is a carbamate prodrug that is activated by carboxylesterase to its active form, MED-B, to exert its DNA alkylation activity. In vitro serum stability studies suggested the efficiencies of hydrolyzing the carbamate-protecting group in αCD70_MED-A followed a rank order of mouse>rat > >monkey>dog~human. Pharmacokinetics of αCD70_MED-A was evaluated in mice, monkeys, and dogs after single intravenous doses. In mice, αCD70_MED-A was cleared rapidly, with no detectable exposures after 15 min following dosing. In contrast, αCD70_MED-A was much more stable in monkeys and dogs. The clearance of αCD70_MED-A in monkeys was 58 mL/d/kg, ~2-fold faster than that in dogs (31 mL/d/kg). The human PK profiles of the total αCD70 and αCD70_MED-A were predicted using allometrically scaled monkeys PK parameters of αCD70 and the carbamate hydrolysis rate constant estimated in dogs. Comparing the predicted and observed human PK from the phase I study, the dose-normalized concentration-time profiles of αCD70_MED-A and the total αCD70 were largely within the 5(th)-95(th) percentile of the predicted profiles.

Abstract LB-252: Enzymology of the mechanism of action for MDX-1203 antibody drug conjugate

MDX-1203 is an antibody drug conjugate under clinical evaluation by Bristol-Myers Squibb. The antibody portion is MDX-1115, a fully human anti-CD70 IgG. The drug portion is MED-2460, a small molecule which itself is composed of the releasable prodrug MED-2284, a cleavable di-peptide linker, and a maleimide reactive group intended to facilitate protein attachment. The mechanism of action of MDX-1203 involves tumor specific delivery and cellular uptake of ADC, followed by the intervention of two different enzymatic pathways. Release of prodrug is accomplished through proteolysis of a citruline-valine di-peptide linker, presumably by Cathepsin B activity in the acidic environment of the lysosome. Activation of released prodrug, MED-2284, occurs in the endoplasmic reticulum via esterase cleavage in the of the piperazine protecting group by the enzyme human Carboxylesterase 2. Michaelis Menten methodologies are used to probe activity of each enzymatic pathway and their relative role in the activity of the drug. Proteolysis is investigated through the use of Human Liver Cathepsin B protease. A kinetic model is constructed for a cysteine modified analogue MED-2460, and then applied to the more complex system involving antibody conjugated drug. Enzymatic activation of released prodrug MED-2284 is investigated with recombinant Human Carboxylesterase 2. For each pathway, the kinetic parameters Km, kcat, and enzymatic efficiency are measured and reported. Parameters are compared in an effort to define the enzymatic rate limiting step in the activation MDX-1203, and define their respective roles in the overall activity of the drug.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-252. doi:1538-7445.AM2012-LB-252

A nonfucosylated human antibody to CD19 with potent B-cell depletive activity for therapy of B-cell malignancies

A human anti-CD19 antibody was expressed in fucosyltransferase-deficient CHO cells to generate nonfucosylated MDX-1342. Binding of MDX-1342 to human CD19-expressing cells was similar to its fucosylated parental antibody. However, MDX-1342 exhibited increased affinity for FcγRIIIa-Phe158 and FcγRIIIa-Val158 receptors as well as enhanced effector cell function, as demonstrated by increased potency and efficacy in antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis assays. MDX-1342 showed dose-dependent improvement in survival using a murine B-cell lymphoma model in which Ramos cells were administered systemically. In addition, low nanomolar binding to cynomolgus monkey CD19 and increased affinity for cynomolgus monkey FcγRIIIa was observed. In vivo administration of MDX-1342 in cynomolgus monkeys revealed potent B-cell depletion, suggesting its potential utility as a B-lymphocyte depletive therapy for malignancies and autoimmune indications.

Glycan optimization of a human monoclonal antibody in the aquatic plant Lemna minor

N-glycosylation is critical to the function of monoclonal antibodies (mAbs) and distinguishes various systems used for their production. We expressed human mAbs in the small aquatic plant Lemna minor, which offers several advantages for manufacturing therapeutic proteins free of zoonotic pathogens. Glycosylation of a mAb against human CD30 was optimized by co-expressing the heavy and light chains of the mAb with an RNA interference construct targeting expression of the endogenous alpha-1,3-fucosyltransferase and beta-1,2-xylosyltransferase genes. The resultant mAbs contained a single major N-glycan species without detectable plant-specific N-glycans and had better antibody-dependent cell-mediated cytotoxicity and effector cell receptor binding activities than mAbs expressed in cultured Chinese hamster ovary (CHO) cells.

Polymyxin B enhances ISS-mediated immune responses across multiple species

The immunostimulatory effects of bacterial DNA on mammalian cells have been localized to unmethylated CpG motifs, and synthetic CpG-containing oligodeoxynucleotides that mimic these effects are known as immunostimulatory sequences (ISS). We have found that the polycationic antibiotic, polymyxin B (PMXB), associates with ISS and serum albumin in vitro and forms microparticles that greatly increase the activity of ISS on plasmacytoid dendritic cells (PDCs). Specifically, ISS/PMXB greatly enhanced IFN-alpha production from PDCs and other activities downstream of IFN-alpha, including IFN-gamma secretion, NK lytic activity, and the expression of genes dependent upon IFN-alpha/IFN-gamma. This amplification was specific for the IFN-alpha pathway since other ISS activities, including B cell proliferation, B cell IL-6 secretion, and PDC maturation, were not affected by PMXB. Both the polycationic peptide and lipophilic fatty acid side chain domains of PMXB, as well as the presence of a third party stabilizing agent such as albumin or Tween 85, were required for particle formation and enhanced ISS activity. The ISS-enhancing activity of PMXB was observed across multiple species (human, primate, and mouse) and in vivo (primate, mouse). These data illustrate the usefulness of formulating ISS with a cationic lipopeptide such as PMXB, which focuses and greatly amplifies the ISS-induced pathway of IFN-alpha-mediated responses.

Induction of tolerance in experimental autoimmune myasthenia gravis with solubilized MHC class II:acetylcholine receptor peptide complexes

Stimulation of T lymphocytes through the T cell receptor in the absence of costimulatory signal(s) induces a state of unresponsiveness to subsequent antigen presentation. We have employed solubilized complexes consisting of rat class II MHC molecules containing an immunodominant peptide of the acetylcholine receptor (AChR alpha 100-116) to induce unresponsiveness in the autoreactive T lymphocytes mediating an animal model of myasthenia gravis. In vitro incubation of rat T cell lines specific for peptide AChR alpha 100-116 with solubilized complexes of MHC II and AChR alpha 100-116 (MHC II:AChR alpha 100-116) rendered the T cells unresponsive to subsequent stimulation by antigen presenting cells and the peptide. T cell lines with a broader specificity to the entire AChR protein pentamer had an 81% reduction in proliferation to AChR following a preincubation with solubilized MHC II:AChR alpha 100-116. Treatment with the solubilized MHC II:AChR alpha 100-116 induced phosphatidylinositol 4,5-bisphosphate hydrolysis, an early signalling event associated with binding to the TCR. Rats primed with AChR and injected intravenously with MHC II:AChR alpha 100-116 had reduced in vitro T cell proliferation to the AChR alpha 100-116 peptide and to whole AChR. Solubilized MHC II:AChR alpha 100-116 injected i.v. into rats exhibiting serological clinical symptoms of experimental autoimmune myasthenia gravis (EAMG) prevented death in 67% of the treated animals, compared to a 0-20% survival rate in all other control groups. These results demonstrate that solubilized MHC II complexed with an immunodominant autoantigenic peptide is tolerogenic and improves the survival rate of rats with EAMG, suggesting the basis for an antigen-specific therapy in autoimmune diseases such as MG.

pH dependent binding of high and low affinity myelin basic protein peptides to purified HLA-DR2

Major histocompatibility complex (MHC) class II molecules are cell surface glycoproteins and are known to display processed antigens on the surface of antigen presenting cells (APC). Within the APC, the loading of processed antigenic peptides to MHC class II molecules is known to take place in the endosomal compartment at acidic pH environment. The present study describes the in vitro effect of pH on binding of four biotinylated myelin basic protein (MBP) peptides to affinity purified HLA-DR2 containing a mixture of DRB1*1501 and DRB5*0101 beta chain. The binding affinity of the selected peptides are in the order of MBP(83-102)Y83 > MBP(124-143) > MBP(143-168) > MBP(1-14). Most of these peptides in association with HLA-DR2 are considered as immunodominant epitopes for human multiple sclerosis autoimmune disorder. One epitope, MBP(1-14), had almost no affinity to purified HLA-DR2 and was used as a control peptide in all binding assays. The quantitation of the bound peptide at various pH was carried out by antibody capture of complexes followed by avidin-alkaline phosphatase detection system. Among four peptides tested, only the highest affinity MBP(83-102)Y83 peptide showed maximum binding to purified HLA-DR2 at acidic pH. Two other epitopes, MBP(124-143) and MBP(143-168), showed maximum binding at basic and neutral pH values, respectively. The binding of only high affinity peptides, MBP(83-102)Y83 and MBP(124-143), was significantly affected by changing the pH of the binding buffer. Such alteration in pH of the binding buffer resulted in 100% occupancy of DR2 with both high affinity MBP peptides. In contrast, no significant increase in binding of the low affinity MBP(143-168) peptide was observed at altered pH values. The specificity of the increased binding of high affinity peptides to HLA-DR2 at optimum pH was demonstrated by competitive binding assays using non-biotinylated peptides. Finally, the stability of various MBP peptide bound complexes was tested at 4 degrees, 25 degrees and 37 degrees C which correlates well with their affinity to HLA-DR2. These results suggest that pH plays an important role in in vitro binding of antigenic peptides and such manipulation of binding conditions can be utilized in generating 100% loaded MHC class II with high affinity antigenic peptides. Since high affinity peptides are generally considered as major immunodominant epitopes, the in vitro pH dependent binding can be utilized in screening immunodominant epitopes of various autoantigens and generating complexes of defined composition.

The role of N-linked oligosaccharides of MHC class II antigens in T cell stimulation

A specific increase in T cell extracellular acidification rate has been demonstrated recently when complexes of purified MHC class II molecules and antigenic peptides interact with T cell receptors (TCRs) on cloned T cells. The present study shows that such measurements of an increase in extracellular acidification rate can be used to evaluate the functional role of various N-linked oligosaccharides of MHC class II antigens. Affinity-purified murine IAk and IAs were deglycosylated in the presence of aspargine-amidase enzyme and were characterized by SDS-polyacrylamide gel electrophoresis. The complete removal of all three N-linked oligosaccharides from the alpha/beta heterodimer was confirmed by four different lectin-linked Western blot analyses. Similar to the native heterodimer, both deglycosylated IAk and deglycosylated IAs were fully capable of binding synthetic antigenic peptides derived from myelin basic protein (MBP). When equivalent amount of glycosylated and deglycosylated class II-peptide complexes were exposed to restricted cloned T cells, identical increases in T cell extracellular acidification rates were observed. The specificity of such increases in extracellular acidification rate was demonstrated by exposing cloned T cells to irrelevant complexes of glycosylated and deglycosylated class II and antigenic peptides. These results show how measurement of extracellular acidification rate can be used to study structure-function correlations of ligand-receptor interactions, and support an earlier observation that N-linked oligosaccharides of murine MHC class II molecules are not involved in either antigenic peptide binding or T cell recognition.

Stimulation of T cells by antigenic peptide complexed with isolated chains of major histocompatibility complex class II molecules

Major histocompatibility complex (MHC) class II molecules are heterodimeric glycoproteins with one alpha and one beta polypeptide chain of similar molecular size. In this report, we describe the binding of an acetylated N-terminal peptide of myelin basic protein, [Ala4]MBP-(1-14), to purified individual alpha and beta chains of murine I-Ak molecules. Purified complexes of isolated single chains and antigenic peptide bind to cloned T cells restricted by I-Ak and [Ala4]MBP-(1-14) tetradecapeptide. The binding is blocked by alpha/beta anti-T-cell receptor (TCR) monoclonal antibody. Cell triggering as measured by an increase in extracellular acidification rate is observed when cloned T cells are exposed to purified complexes of isolated chains and antigenic peptide. This increase in the extracellular acidification rate is antigen specific and MHC-restricted, as chains alone or irrelevant chain-peptide complexes do not trigger an increase in the metabolic acidification rate. These results together demonstrate that in vitro cloned T cells are triggered by complexes of specific antigenic peptides and isolated individual chains of their cognate MHC proteins.

Purified beta-chain of MHC class II binds to CD4 molecules on transfected HeLa cells

The initial event triggering the activation of Th cells occurs when the TCR interacts with antigenic peptide in the context of the MHC II on APC. Various T cell accessory molecules including CD4, CD28, and LFA-1 participate and facilitate the activation event. Although some evidence for the interaction of MHC II and CD4 is available, the site of MHC class II (alpha-chain, beta-chain, or both chains) for CD4 interaction has not yet been clearly defined. Results from different laboratories had indicated the involvement of alpha 1, beta 1, and beta 2 domains of MHC class II molecules in CD4 interaction. Recently, a conserved site of DR beta 2 domain has been identified that involves CD4 interaction that is analogous to MHC class I binding site for CD8 molecule. In this report, direct binding of affinity-purified HLA-DR2 dimer and its isolated alpha- and beta-chains to CD4 was studied using a CD4-transfected HeLa cell line. Preferential binding of the beta-chain and intact MHC II dimer to the CD4-transfected cells was observed and found to be specifically inhibited by anti-CD4 mAb. In contrast, the isolated alpha-chain of HLA DR2 did not show significant binding to CD4-transfected cells. Complexes of radiolabeled DR2 dimer or beta-chain alone with an immunodominant epitope from myelin basic protein (83-102) did not show any further increase in binding of these molecules. Binding of the beta-chain to CD4+ cells was markedly inhibited by a DR beta 1 peptide (35-46) and was partially inhibited by a DR beta 2 peptide (134-148) of MHC class II molecule. These results suggest the involvement of at least two conserved regions of the beta polypeptide chain of MHC class II in CD4 interaction. Because in our experiments transfected cells lack TCR molecules and the binding of DR2 to the CD4-transfected cells was unaffected by added antigenic peptide, it is possible that the interaction of MHC class II to CD4 is independent of TCR occupancy.

Purified beta-chain of MHC class II binds to CD4 molecules on transfected HeLa cells

The initial event triggering the activation of Th cells occurs when the TCR interacts with antigenic peptide in the context of the MHC II on APC. Various T cell accessory molecules including CD4, CD28, and LFA-1 participate and facilitate the activation event. Although some evidence for the interaction of MHC II and CD4 is available, the site of MHC class II (alpha-chain, beta-chain, or both chains) for CD4 interaction has not yet been clearly defined. Results from different laboratories had indicated the involvement of alpha 1, beta 1, and beta 2 domains of MHC class II molecules in CD4 interaction. Recently, a conserved site of DR beta 2 domain has been identified that involves CD4 interaction that is analogous to MHC class I binding site for CD8 molecule. In this report, direct binding of affinity-purified HLA-DR2 dimer and its isolated alpha- and beta-chains to CD4 was studied using a CD4-transfected HeLa cell line. Preferential binding of the beta-chain and intact MHC II dimer to the CD4-transfected cells was observed and found to be specifically inhibited by anti-CD4 mAb. In contrast, the isolated alpha-chain of HLA DR2 did not show significant binding to CD4-transfected cells. Complexes of radiolabeled DR2 dimer or beta-chain alone with an immunodominant epitope from myelin basic protein (83-102) did not show any further increase in binding of these molecules. Binding of the beta-chain to CD4+ cells was markedly inhibited by a DR beta 1 peptide (35-46) and was partially inhibited by a DR beta 2 peptide (134-148) of MHC class II molecule. These results suggest the involvement of at least two conserved regions of the beta polypeptide chain of MHC class II in CD4 interaction. Because in our experiments transfected cells lack TCR molecules and the binding of DR2 to the CD4-transfected cells was unaffected by added antigenic peptide, it is possible that the interaction of MHC class II to CD4 is independent of TCR occupancy.

Preparative-scale purification and characterization of MHC class II monomers

The MHC class II molecule is a heterodimeric glycoprotein consisting of one alpha and one beta polypeptide chain of almost identical molecular size. Recently it has been shown by others, and confirmed in our laboratory, that isolated monomers of murine MHC II molecules are capable of binding antigenic peptides like the alpha/beta intact heterodimer. In addition, preliminary results from our laboratory indicate that isolated single chain-peptide complexes of murine MHC class II molecules are capable of stimulating cloned T cells in an antigen specific manner. These results prompted us to isolate relatively large quantities of individual alpha and beta subunits of MHC II molecules for further in vitro and in vivo studies. Isolation of alpha and beta monomers proved to be difficult using conventional chromatographic methods. In this report we describe micro-preparative and preparative continuous flow electrophoresis methods by which milligram quantities of MHC II subunits can be purified. An optimal condition for the dissociation of heterodimeric MHC II into alpha and beta monomers was identified, and separation of human HLA DR2 and murine IAs monomers was accomplished. Both methods offer the resolving power of gel electrophoresis with the convenience of continuous sample elution. Purified MHC II subunits obtained by these methods were tested for their ability to bind antigenic peptides. Results presented in this study indicate that monomeric subunits of both human HLA-DR2 and murine IAs are equally active in specific binding of antigenic peptides like the native heterodimer.

N-linked oligosaccharides of murine major histocompatibility complex class II molecule. Role in antigenic peptide binding, T cell recognition, and clonal nonresponsiveness

To evaluate the functional role of the N-linked oligosaccharides of major histocompatibility complex (MHC) class II molecules, affinity-purified murine IAs class II molecules were deglycosylated in the presence of asparagine amidase enzyme. The deglycosylated IAs molecules were characterized by 12% SDS-polyacrylamide gel analysis under reduced and native conditions and the complete enzymatic removal of all three N-linked sugar components from the alpha/beta heterodimer was confirmed by lectin-link Western blot analysis. Like the native IAs molecules, the deglycosylated IAs molecules were fully capable of binding an antigenic peptide from myelin basic protein MBP(89-101). The kinetics of dissociation of preformed complexes of IAs.MBP(89-101) and deglycosylated IAs.MBP(89-101) were compared at 4 and at 37 degrees C. Both complexes were equally stable at 4 degrees C; however, at 37 degrees C the deglycosylated IAs.MBP(89-101) complexes showed an increased rate of dissociation as compared with the native IAs.MBP(89-101) complexes. When tested for their ability to recognize the T cell receptor on T cells, both complexes bound to cloned HS-1 T cells that recognize and respond to IAs.MBP(89-101). Finally, the complexes of deglycosylated IAs.MBP(89-101) were tested for the induction of in vitro nonresponsiveness and compared with native IAs.MBP(89-101) complexes. Both complexes were capable of inducing 95-100% nonresponsiveness in a proliferation assay. These results suggest that the N-linked oligosaccharide of MHC class II molecules may not be essential for either antigenic peptide binding or T cell recognition. In addition results obtained here provide evidence that the carbohydrate moities of MHC class II molecules may not be involved in induction of T cell clonal anergy.

In vitro maximum binding of antigenic peptides to murine MHC class II molecules does not always take place at the acidic pH of the in vivo endosomal compartment

Presentation of Ag to the T cell requires binding of specific peptide fragments of the Ag to MHC II molecules. The ability of a peptide to bind to MHC class II appears to be pH dependent. Recent reports indicate that the binding of peptide to MHC class II molecules takes place primarily within an endosomal compartment of the cell at around pH 5. In this study, we have explored the in vitro pH dependence of peptide binding to different haplotypes of murine MHC class II molecules. The binding of peptides to MHC II was analyzed and quantitated by silica gel TLC, using radiolabeled peptides. The MBP peptide fragments, MBP(1-14)A4 and MBP(88-101)Y88, bound maximally at pH 8 to IAk and IAs, respectively. The binding of PLP peptide fragment, PLP(138-151)Y138, to IAs was maximal at around neutral pH. The maximum binding of an OVA peptide fragment, OVA(323-340)Y340, to IAd, was found to occur at pH 6. Results presented in this report thus suggest that the in vitro maximum binding of peptide is pH dependent and does not always occur at pH 5. The optimum pH range for maximum binding may depend on the nature and net charge of the peptide and its interaction with MHC class II molecules.

In vitro maximum binding of antigenic peptides to murine MHC class II molecules does not always take place at the acidic pH of the in vivo endosomal compartment

Presentation of Ag to the T cell requires binding of specific peptide fragments of the Ag to MHC II molecules. The ability of a peptide to bind to MHC class II appears to be pH dependent. Recent reports indicate that the binding of peptide to MHC class II molecules takes place primarily within an endosomal compartment of the cell at around pH 5. In this study, we have explored the in vitro pH dependence of peptide binding to different haplotypes of murine MHC class II molecules. The binding of peptides to MHC II was analyzed and quantitated by silica gel TLC, using radiolabeled peptides. The MBP peptide fragments, MBP(1-14)A4 and MBP(88-101)Y88, bound maximally at pH 8 to IAk and IAs, respectively. The binding of PLP peptide fragment, PLP(138-151)Y138, to IAs was maximal at around neutral pH. The maximum binding of an OVA peptide fragment, OVA(323-340)Y340, to IAd, was found to occur at pH 6. Results presented in this report thus suggest that the in vitro maximum binding of peptide is pH dependent and does not always occur at pH 5. The optimum pH range for maximum binding may depend on the nature and net charge of the peptide and its interaction with MHC class II molecules.